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Patented Nov; 23,- 1897.

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IIIII Patented Nov. 23

RESISTANCE DEVICE.

G. K. CUMMINGS.

(No Model.)

Darren ST TES PATENT Creme.

GEORGE K. CUMMINGS, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE GRAPHITE RIIEOSTAT COMPANY, OF SAME PLACE.

RESISTANCE DEVICE.

SPECIFICATION forming part of Letters Patent No. 593,988, dated November 23, 1897.

Application filed December 23,1895. Serial No. 573,041. (No model.)

To all whom it may concern view on the line4c4 of Fig. 3. Fig. 5 is a sec- Be it known that I, GEORGE K. CUMMINGS, tional view on the line 5 5 of Fig. 3, and Fig.

acitizen of the United States, residing in Ohi- 6 is a detailview of a modified form of a cago, in the county of Cook and State of Illimember. 5

5 nois,have invented certainnew and usefulIm- Referring to the drawings, in which like provements in Resistance Devices, of which letters of reference denote corresponding the following is afull, clear, and exact descripparts in all the figures, A designates the front tion, reference being had to the accompanyplate, which is secured to the frame B by ing drawings, forming apart of this specificameans of the screw-rods b at the corners of IO tion. said frame. Two or more transverse rods C My invention relates to certain new and useare secured to opposite sides of said frame,

ful improvements in electrical resistance deand movable cross-pieces D E are mounted on vices which may be employed for regulating said rods. A rack-bar F is secured at its an electric current by offering more or less reends to the cross-pieces and is arranged to r 5 sistance to its passage or used as an electric mesh with a ratchet-wheel f, which is mountheating device. ed on a suitable shaft f and is operated by The object of the invention is to provide a means of the .wheel G. resistance device composed of a number of re- In the drawings I have illustrated the resistance members the total resistance of which sistance members in the form of tubes or cyl- 7o 20 can be varied by slight gradations, and a furinders J, which is a convenient construction,

ther object is to provide a simple and inexbut my invention is not limited to any parpensive construction and arrangement of ticular form or construction of the members, parts which can be readily manipulated to acfor it is obvious that many other forms may complish the results sought for. be employed. For example, I may employ a 25 WVith these and other ends in view the inrod of some resistance material and a box vention contemplates anumber of resistance containing mercury adapted to be adjusted members, one form of which is filled with a on said rod, one wire being connected to the suitable resistance material and two termibox and the other to the rod in some suitable nals arranged in the resistance material of manner, or instead of the box containing mer- 8o 30 each member, one of which terminals is adaptcury I may use a brush. The members may ed to be adjusted in the material, whereby be embodied in many other forms, which it is the total resistance may be permanently vaunnecessary for me to mention here. The ried by connecting said members in series, in tubes J are mounted'between the cross-pieces multiple, in multiple series, or in series mul- D E, and the ends of the tubes are fitted in 5 tiple, and yet the total resistance may also be recesses g in the faces of the cross-pieces, be-

readily varied irrespective of the method of ing preferably provided with a screw-thread connecting the members. for this purpose. I may employ any number The term member as used by me in of these tubes more than one, and it is not at this specification is to be understood as inall essential that they should be of any par- 4o dicating a portion of a total resistance that ticular form or configuration, the only rehas attached thereto two electric connections, quirement being that they shall contain a through which such portion or member may sufficient quantity of resistance material for have electrical connection with the circuit. the purposes of the invention. The tubes The invention consists also of certain other are filled with suitable resistance material J,

45 features of construction and details which and I have found that powdered graphite,

will be fully described hereinafter. from fifty per cent. to ninety per cent. pure,

In the accompanying drawings, forming a is the preferred material, as it accomplishes part of this application, Figure l is a front the results of my invention in asuperior manview of the device. Fig. 2 is a side elevaner. I would have it understood, however, I00

50 tion. Fig. 3 is a view, partly in section,with that I do not hereby limit myself to any parthe front plate removed. Fig. 4 is a sectional ticular resistance material.

Each of the members and the parts connected therewith are substantially alike, and I will therefore only describe one of them. A red II, which forms one of the terminals, ex tends into one end of the tube, and it is secured at its other end to a stationary crosspiece I at one side of the frame. It will thus be observed that as the wheel G is operated the ratchet-wheel f, meshin g with the rack F, moves the two cross-pieces D E on the rods 0, and the tube J is adjusted farther on or off of the long terminal rod II. Referring particularly to Fig. 3 of the drawings, if the ratchet-wheel f is turned to the left the short rod 7t will be moved farther away from the long red II, and the resistance afforded by the material between the terminals is thereby increased, and if the wheelf is turned to the right the rod h is brought closer to the rod II and the resistance decreased.

Although I have shown and described the tubes as arranged and adapted to be adjusted on the rods II, it is obvious that the crosspieees D E may be made stationary and the cross-piece I movable, so that the rods II can be adjusted in the tubes.

As hereinbefore stated, the tubes J may be of any form or shape adapted to the particular purposes for which they are intended, and they may be cast or fashioned with irregular exteriors to increase the heat-radiating surfaces. They are preferably made of metal and lined or coated with enamel or other in sulating substance. The electric current is carried to the terminals in a suitable manner, and it is regulated by the resistance offered by the amount of granulated or powdered material between the adjacent ends of the rods h II, the density of said material being substantially constant. The shorter rod 71, does not move into the tube, but when the cross-pieces D E are operated the tube is moved onto the long red II, and the resistance of the material between the contact-rods is increased or decreased in exact ratio to the length of the movement of the tube. It is essential that there should be sufficient resistance material in the tube, so that a sufticient carrying capacity may at all times be provided between the ends of the terminals, whether they be close together or far apart.

The contact-rods may be connected in series, in multiple, in multiple series, or in series multiple, as desired, and in any combination where a number of members are employed each member thus bears an equal share of the total energy consumed in resistanee.

The wheel or handle G, which may be of any desired construction, is preferably constructed so that one turn or revolution there of will move the tube throughout its entire limit of movement, but this of course may be varied as desired.

I have shown in the drawings a number of tubes, all of which are constructed alike, and

any number of them may be employed. In order that the device may not be too bulky in size, I prefer to proportion the parts for a comparatively high temperature of the mem bers and to use a resistance material not only of a high resistance, but one which will not easily fuse and which is capable of remaining unchanged in its chemical and structural formation upon the application of very high temperatures.

As the actual radiatin g-surfaees of the tubes are protected by the frame, it is evident that they maybe safely heated to a very high temperature without danger of tire, the exterior of the device being heated only by conduction by the air-currents passing through the openings in the sides K of the frame.

By the use of my improved construction I entirely avoid the sparking and arcing at the contactpoints which usually occur in devices of this character, as well as the liability of forming rough and uneven electrh'ealter1ni nals, which tend to decrease the brillianey of the light supplied by the current, and the gradations are so uniform and small and the decrease of brilliancy so gradual that the eye cannot detect any jump or unevenness of light when the resistance is increased or decrcz'ised, but merely an even gradation.

It will be observed that in decreasing the total resistance of the device it is unneccssary to cut out any member whereby the practical heat-radiating surface of the device is increased, and that portion of the member which is not active electrically is in. the best possible juxtaposition to the active portion for the purpose of aiding in dissipating the heat from the active portion.

In Fig. 6 I have illustrated another of the many forms of members which may be em ployed in connection with my invention, which contemplates the employment of a l'up uid or semiliquid resistance material J, in which the terminal. If is adapted to be adjusted after the manner of a'plunger. The construction of parts and operation of this device are substantially similar in every way to that hereinbefore described and I will not enter into a detailed description thereof.

Nhere large currents are required to be passed through the device, I 11nd it desirable to connect the members in. multiple or multiple series, in which cases the passage of the current does not depend upon any one eontact, but it divides its path proportionally to any defects that may occur in the electro mechanical construction of the device.

By using a number of resistance members I am able to provide a device in which all of said members may be adjusted to provide a total gradation of resistance, and I am therefore also able to construct my device in a convenient and advantageous manner, so that it will not be likely to burn out. If desired, one or more of the members may be entirely out out of the circuit.

I am aware that changes in the form, and

proportion of parts and details of construction of the invention may be made without departing from the spirit or sacrificing the advantages thereof, and I therefore reserve the right to make all such changes as fairly fall Within the scope and spirit of the invention.

" Having thus described my invention, what I claim, and desire to secure by Letters Patcut, is--- 1. In an electrical resistance device, the combination with the cross-pieces, of the terminal rods supported on said cross-pieces,two of said cross-pieces being movable, a number of tubes containing electric resistance material of constant density supported between the movable cross-pieces, and means for adjusting the tubes on some of the terminal rods, substantially as and for the purpose described.

2. The combination of a frame, the crosspieces movably secured in said fra1ne,= a number of tubes arranged between said crosspieces and containing suitable resistance material, a terminal rod secured in one end of each tube, and another terminal rod arranged in the other end of each tube, and means for moving said cross-pieces to adjust the tubes on some of said terminal rods, substantially as described.

3. The combination of a frame, the crosspieces movablysecured in said frame, a number of tubes arranged between said crosspieces and containing suitable resistance material, a terminal rod secured in one end of each tube, another terminal rod arranged in the other end of each tube, arack-bar secured between said cross -pieces, and a ratchetwheel arranged in engagement with said rackbar and adapted to be operated to move the cross-pieces, substantially as described.

t. The combination of a frame, the rods se-v cured in said frame, the movable cross-pieces mounted on said rods, a number of tubes secured between said cross-pieces and containing an electric resistance material, a terminal rod rigidly secured in one end of each tube, a stationary cross-piece, a terminal rod arranged in the other end of each tube and secured to the stationary cross-piece, a rack-bar connecting the movable cross-pieces, a ratchet-wheel arranged in engagement with said rack-bar, and a handle for operating said ratchet-Wheel whereby thetubes may be adjusted to increase or decrease the resistance between the ends of the terminals, substantially as described.

GEORGE K. CUMMINGS.

Witnesses:

WM. 0. BELT, M. E. SHIELDs. 

